U.S. patent number 6,682,307 [Application Number 09/979,401] was granted by the patent office on 2004-01-27 for sealing system for a rotor of a turbo engine.
This patent grant is currently assigned to Siemens Aktiengesellschaft. Invention is credited to Peter Tiemann.
United States Patent |
6,682,307 |
Tiemann |
January 27, 2004 |
Sealing system for a rotor of a turbo engine
Abstract
A turbomachine, in particular a gas turbine, includes a rotor
which extends along an axis of rotation. The rotor includes a
circumferential face, which is defined by the outer radial boundary
surface of the rotor, and a receiving structure. Additionally, it
includes a first rotor blade and a second rotor blade, which each
have a blade root and a blade platform. The blade platform of the
first rotor blade and the blade platform of the second rotor blade
adjoin one another, and a space is formed between the blade
platforms and the circumferential face. A sealing system is
provided on the circumferential face in the space, the sealing
system including a labyrinth sealing system.
Inventors: |
Tiemann; Peter (Witten,
DE) |
Assignee: |
Siemens Aktiengesellschaft
(Munich, DE)
|
Family
ID: |
7908072 |
Appl.
No.: |
09/979,401 |
Filed: |
February 28, 2002 |
PCT
Filed: |
May 15, 2000 |
PCT No.: |
PCT/DE00/01550 |
PCT
Pub. No.: |
WO00/70191 |
PCT
Pub. Date: |
November 23, 2000 |
Foreign Application Priority Data
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|
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May 14, 1999 [DE] |
|
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199 22 256 |
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Current U.S.
Class: |
416/193A;
416/215; 416/216; 416/219R; 416/95; 416/96R; 416/248 |
Current CPC
Class: |
F01D
11/006 (20130101); F01D 11/008 (20130101) |
Current International
Class: |
F01D
11/00 (20060101); F01D 005/30 () |
Field of
Search: |
;416/193A,219R,22R,221,248,500,215,216,218,190,95,96R,97R |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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26 58 345 |
|
Jun 1978 |
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DE |
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198 10 567 |
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Sep 1998 |
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DE |
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905582 |
|
Sep 1962 |
|
EP |
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1 491 557 |
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Nov 1977 |
|
EP |
|
0 761 930 |
|
Mar 1997 |
|
EP |
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2 603 333 |
|
Mar 1988 |
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FR |
|
1457417 |
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Dec 1976 |
|
GB |
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2 280 478 |
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Feb 1995 |
|
GB |
|
Other References
Patent Abstract of Japan, Oct. 13, 1980, vol. 4/No. 183. .
"Vorrichtung zum Sichern der Schaufeln von Stromungsmaschinen",
Daimler-Benz Aktiengesellschaft Stuttgart-Unterturkheim, Mar. 27,
1962..
|
Primary Examiner: Verdier; Christopher
Attorney, Agent or Firm: Harness, Dickey & Pierce,
P.L.C.
Claims
What is claimed is:
1. A turbomachine including a rotor which extends along an axis of
rotation, comprising: a circumferential face, defined by an outer
radial boundary surface of the rotor; a receiving structure; a
first rotor blade and a second rotor blade, each including a blade
root and a blade platform which adjoins the blade root, the blade
root of the first rotor blade and the blade root of the second
rotor blade being inserted into the receiving structure such that
the blade platform of the first rotor blade and the blade platform
of the second rotor blade adjoin one another, wherein a space is
formed between the blade platforms and the circumferential face;
and a sealing system is provided on the circumferential face in the
space, the sealing system including at least one labyrinth sealing
system and a circumferential-face central region, bordered in an
axial direction by a first circumferential-face edge and a second
circumferential-face edge, opposite the first circumferential edge
along the axis of rotation, being formed on the circumferential
face, wherein the sealing system including the labyrinth sealing
system is arranged at least partially on the circumferential-face
central region.
2. The turbomachine as claimed in claim 1, wherein the rotor
includes a rotor disk, which includes the circumferential face and
the receiving structure, the receiving structure including a first
rotor-disk groove and a second rotor-disk groove which is at a
distance from the first rotor-disk groove in the circumferential
direction of the rotor disk, and wherein the blade root of the
first rotor blade is inserted into the first rotor-disk groove and
the blade root of the second rotor blade is inserted into the
second rotor-disk groove.
3. The turbomachine as claimed in claim 1, wherein the sealing
system includes a sealing element which extends in the
circumferential direction.
4. The turbomachine as claimed in claim 3, further comprising: at
least one further sealing element which extends in the
circumferential direction and is arranged at an axial distance from
the sealing element.
5. The turbomachine as claimed in claim 3, wherein at least one of
the sealing element and a further sealing element includes, on an
outer radial end thereof, a sealing point.
6. The turbomachine as claimed in claim 3, wherein the labyrinth
sealing system includes at least one of the sealing element and a
further sealing element.
7. The turbomachine as claimed in claim 1, wherein the labyrinth
sealing system is designed as a labyrinth gap sealing system.
8. The turbomachine as claimed in claim 1, wherein the labyrinth
sealing system is produced integrally.
9. The turbomachine as claimed in claim 1, further comprising: a
gap sealing element for sealing a substantially axially extending
gap, the gap being formed between the blade platform of the first
rotor blade and the blade platform of the second rotor blade and
being in flow communication with the space.
10. The turbomachine as claimed in claim 9, wherein the gap sealing
element is produced by a metal gap sealing plate including a
gap-sealing edge which engages in the gap under the action of
centrifugal force and closes off the gap.
11. The turbomachine as claimed in claim 9, wherein the gap sealing
element is produced from a highly heat-resistant material.
12. The turbomachine as claimed in claim 9, wherein the gap sealing
element radially adjoins the sealing system.
13. The turbomachine as claimed in claim 1, wherein the
turbomachine is designed as a gas turbine.
14. The turbomachine of claim 1, wherein the turbomachine is a gas
turbine.
15. The turbomachine as claimed in claim 2, wherein the sealing
system includes a sealing element which extends in the
circumferential direction.
16. The turbomachine as claimed in claim 4, wherein at least one of
the sealing element and the further sealing element includes, on an
outer radial end thereof, a sealing point.
17. The turbomachine of claim 5, wherein the sealing point is a
knife edge.
18. The turbomachine of claim 8, wherein the labyrinth sealing
system is produced by removing material from the rotor disk.
19. The turbomachine as claimed in claim 4, wherein the labyrinth
sealing system includes at least one of the sealing element and the
further sealing element.
20. The turbomachine as claimed in claim 5, wherein the labyrinth
sealing system includes at least one of the sealing element and the
further sealing element.
21. The turbomachine as claimed in claim 10, wherein the gap
sealing element is produced from a highly heat-resistant
material.
22. The turbomachine of claim 11, wherein the gap sealing element
is produced from at least one of a nickel-base alloy and a cobalt
based alloy.
23. The turbomachine of claim 21, wherein the gap sealing element
is produced from at least one of a nickel-base alloy and a cobalt
based alloy.
24. The turbomachine as claimed in claim 10, wherein the gap
sealing element radially adjoins the sealing system.
25. The turbomachine as claimed in claim 11, wherein the gap
sealing element radially adjoins the sealing system.
Description
This application is the national phase under 35 U.S.C. .sctn.371 of
PCT International Application No. PCT/DE00/01550 which has an
International filing date of May 15, 2000, which designated the
United States of America, the entire contents of which are hereby
incorporated by reference.
FIELD OF THE INVENTION
The invention generally relates to a turbomachine. In particular,
it relates to a gas turbine, preferably one including a sealing
system for a rotor which extends along an axis of rotation. Even
more preferably, the rotor includes a first rotor blade and a
second rotor blade which adjoins the first rotor blade in the
circumferential direction of the rotor.
BACKGROUND OF THE INVENTION
Rotatable rotor blades of turbomachines, for example of turbines or
compressors, are secured in various designs over the entire
circumference of the circumferential face of a rotor shaft which is
formed, for example, by a rotor disk. A rotor blade usually has a
main blade, a blade platform and a blade root with a securing
structure which is fitted to the circumferential face of the rotor
shaft in a suitably complementary recess, which is produced, for
example, as a circumferential groove or an axial groove, so that
the rotor blade is fixed in this way.
For design reasons, after the rotor blades have been inserted into
the rotor shaft, gaps are formed by the regions which adjoin one
another, and in operation of a turbine these gaps give rise to
leaking flows of coolant or of a hot action fluid which drives the
rotor. Such gaps occur, for example, between two adjacent blade
platforms of rotor blades which adjoin one another in the
circumferential direction and between the circumferential face of
the rotor shaft and a blade platform which radially adjoins the
circumferential face. To limit the possible leaking flows, such as
for example the escape of coolant, e.g. of cooling air, into the
flow channel of a gas turbine, intensive searches are being made
for suitable sealing concepts which are able to withstand the
temperatures which occur and the mechanical load caused by the
considerable centrifugal forces acting on the rotating system.
DE 198 10 567 A1 has disclosed a sealing plate for a rotor blade of
a gas turbine. If cooling air which is fed to the rotor blade
escapes into the flow channel, this leads, inter alia, to a
reduction in the efficiency of the gas turbine. The sealing plate,
which is inserted into a gap between the blade platforms of
adjacent rotor blades, is intended to prevent the leaking flows
caused by the escape of cooling air. The sealing is produced not
only by said sealing plate but also by various sealing pins which
are likewise fitted between the blade platforms of two adjacent
rotor blades. A multiplicity of sealing elements are required in
order to achieve the desired sealing action preventing cooling air
from escaping from the adjacent blade platforms.
U.S. Pat. No. 5,599,170 has described a sealing concept for a rotor
blade of a gas turbine. A substantially radially extending gap and
a substantially axially extending gap are formed by two rotor
blades which adjoin one another and are attached to the
circumferential face of a rotor disk which can rotate about an
axis. A sealing element seals the radial gap and, at the same time,
the axial gap. For this purpose, the sealing element is inserted
into a cavity which is formed by the blade platforms of the rotor
blades. The sealing element has a first sealing face and a second
sealing face which respectively adjoin the axial gap and the radial
gap.
Moreover, the sealing element has a thrust face which extends
obliquely with respect to the radial direction. The thrust face
directly adjoins a reaction face which is formed as a partial area
of a moveable reaction element arranged in the cavity. The sealing
action is produced by the centrifugal forces acting on the moveable
reaction element as a result of the rotation of the rotor disk. The
reaction element transmits to the inclined thrust face a force, the
radially directed component of which acts on the sealing element,
so that the first sealing face seals the axial gap, while the
axially oriented component of the force on the sealing element
leads to the second sealing face sealing the radial gap. This
sealing concept is unable to prevent cooling air from escaping into
the flow passage of the gas turbine along the circumferential face
of the rotor disk through gaps which are formed between the
circumferential face of the rotor disk and a blade platform of a
rotor blade which radially adjoins the circumferential face.
Similarly complex arrangements with one or more sealing elements,
as are described in DE 198 10 567 A1 or U.S. Pat. No. 5,599,170,
are also used in a turbomachine to prevent a flowing, hot action
fluid, e.g. a hot gas or vapor, from entering gap regions and
spaces in a rotor. Penetrating action fluid of this type could lead
to considerable damage to the rotor blade. To reduce this risk,
generally a plurality of sealing elements are inserted into the
blade platform on that side of the blade platform of the rotor
blade which faces the flow of action fluid.
EP 0 761 930 A1 and GB 905,582 each describe a turbomachine with a
turbine rotor. The turbine rotor is in this case of disk design and
is composed of individual rotor disks which are arranged axially
adjacent to one another. Rotor blades, which are each secured by
means of their blade root in an axial groove in the rotor disk,
e.g. an axial fir-tree groove or a hammerhead groove, are arranged
on the circumference of the rotor disks. Axial fixing of the rotor
blades in the blade root/groove region is effected by securing
plates which are mounted in a fixed position on the end sides of
the rotor disks. The end-side securing plates can also be used to
achieve a certain sealing action with respect to possible
penetration of action fluid, for example, a hot gas, in the blade
root/groove region. However, the securing plates serve primarily to
fix the rotor blades in the axial direction.
GB-A-2 280 478 has disclosed a gas-turbine rotor which has sealing
arrangements. In one configuration, the sealing arrangement has
sealing points which are arranged on the rotor surface and bear in
a sealed manner against a radially inwardly arranged sealing face
of a turbine guide vane.
U.S. Pat. No. 4,878,811 has disclosed a rotor blade arrangement of
an axial compressor. The rotor blade arrangement is produced by a
rotor disk with circumferential groove, a multiplicity of
compressor rotor blades being secured in the groove over the entire
circumference of the rotor disk, so that a ring of rotor blades is
formed. Furthermore, a sealing ring is arranged in a sealing groove
over the entire circumference of the rotor disk, resulting in a
substantially sealed connection between the rotor disk and the
platform of the rotor blade.
SUMMARY OF THE INVENTION
The invention is based on an object of providing a highly efficient
sealing system for a turbomachine, preferably one including a rotor
which extends along an axis of rotation and has a first rotor blade
and a second rotor blade which adjoins the first rotor blade in the
circumferential direction of the rotor. The sealing system is in
particular intended to actively limit the possible leaking flows
through gap regions and spaces of the rotor and to be able to
withstand the thermal and mechanical loads which occur. In
addition, the sealing system is preferably to be designed in such a
way that it can be produced as easily as possible and can be
employed for various rotors.
According to the invention, an object is achieved by a
turbomachine, preferably a gas turbine, including a rotor which
extends along an axis of rotation, comprising a circumferential
face, which is defined by the outer radial boundary surface of the
rotor, and a receiving structure, as well as a first rotor blade
and a second rotor blade, which each have a blade root and a blade
platform which adjoins the blade root, the blade root of the first
rotor blade and the blade root of the second rotor blade being
inserted into the receiving structure, so that the blade platform
of the first rotor blade and the blade platform of the second rotor
blade adjoin one another, and a space is formed between the blade
platforms and the circumferential face, in which turbomachine a
sealing system is provided on the circumferential face in the
space, the sealing system having at least one labyrinth sealing
system and a circumferential-face central region, which is bordered
in the axial direction by a first circumferential-face edge and a
second circumferential-face edge, which lies opposite the first
circumferential-face edge along the axis of rotation, being formed
on the circumferential face, and in that the sealing system having
the labyrinth sealing system is arranged at least partially on the
circumferential-face edge.
The invention is based on the consideration that when a
turbomachine is operating, the rotor is exposed to a flowing hot
action fluid. As a result of the expansion, the hot action fluid
applies work to the rotor blades and sets them in rotation about
the axis of rotation. Therefore, the rotor with the rotor blades is
subject to very high thermal and mechanical loads, in particular on
account of the centrifugal forces which occur as a result of the
rotation.
A coolant, e.g. cooling air, which is usually fed to the rotor
through suitable coolant feeds, is used to cool the rotor and in
particular the rotor blades. In this case, leaking flows of both
coolant and hot action fluid--what are known as gap losses--may
occur in the space. A space is in this case formed by the
circumferential face, which in this case is defined by the outer
radial boundary surface of the rotor and by the platform, arranged
radially outside the circumferential face, of rotor blades which
are arranged next to one another in the circumferential direction
of the rotor.
These leaking flows have a very disadvantageous effect on the
cooling efficiency and the mechanical installation strength (quiet
running and creep rupture strength) of the rotor blades in the
receiving structure of the circumferential face. In this context,
leaking flows which are oriented along the axis of rotation (axial
leaking flows), for example along the circumferential face, are of
particular importance. Furthermore, leaking flows perpendicular to
the axis of rotation (radial leaking flows), which are directed
along a radial direction and therefore substantially perpendicular
to the circumferential face, should also be borne in mind.
The invention demonstrates a new way of effectively sealing a rotor
with a first rotor blade and with a second rotor blade which
adjoins the first rotor blade in the circumferential direction of
the rotor in a turbomachine with respect to possible leaking flows.
The arrangement takes account of both axial and radial leaking
flows. This is achieved by the fact that the sealing system having
a labyrinth sealing system is arranged in the space on the
circumferential face of the rotor, which face is defined by the
radially outer boundary surface of the rotor. As a result of the
configuration described, the sealing system seals the space which
is formed between the blade platforms and the circumferential face.
The space extends in the radial and axial and circumferential
directions of the rotor.
In this case, the axial extent of the gap is generally dominant,
while its extent in the circumferential direction is greater than
the radial dimension. The precise geometry of the space is
determined by the specific configuration of the mutually adjacent
blade platforms and of the circumferential face. The design of the
sealing system described, which has a labyrinth sealing system, can
be individually adapted to the particular geometry and requirements
with regard to the leaking flows which are to be restricted, the
provision of a labyrinth sealing system being particularly
effective for sealing the space.
The action of a labyrinth sealing system is based on the most
effective possible restriction of the hot action fluid and/or of
the coolant in the sealing system and a resulting substantial
prevention of an axially directed leaking flow (leak mass flow)
through the space. In this case, a residual leaking flow through
existing sealing gaps, as generally occur with labyrinth gap seals,
for example, can be calculated taking account of the so-called
bridging factor. With the same flow parameters upstream and
downstream of the seal and identical principal dimensions of the
labyrinth sealing system (sealing gap diameter, sealing gap width,
overall axial length of the seal), labyrinth gap sealing systems,
which are also referred to as look-through seals, compared to
so-called tongue-and-groove sealing systems have a leaking flow
through the sealing gap which is up to 3.5 times greater. However,
on account of the sealing gap which remains, labyrinth gap sealing
systems have the considerable advantage over the tongue-and-groove
sealing systems that they themselves are suitable for considerable
thermally and/or mechanically induced relative expansions in the
rotor.
A significant advantage over conventional sealing concepts results
from the labyrinth sealing system being arranged on the
circumferential face. As a result, it is possible for the labyrinth
sealing system to directly adjoin the circumferential face, so that
a sealing action is produced. This is particularly suitable for
preventing leaking flows in the axial direction along the
circumferential face. By way of example, even the penetration of a
hot action fluid, e.g. the hot gas in a gas turbine, into the space
is substantially prevented and an axially directed flow in the
space along the circumferential face is considerably reduced. This
protects the material of the rotor, in particular the material of
the blade platforms, from the high temperatures and the possible
oxidizing and corrosive influences of the hot action fluid. In the
radial direction the sealing system having the labyrinth sealing
system may be dimensioned in such a way that it directly adjoins
the adjacent blade platforms and a sealing action is achieved. In
this way, axial leaking flow is virtually completely prevented, or
at least is significantly suppressed.
Temperature gradients in the region of the rotor blade attachment
area are avoided by preventing leaking flows of hot action fluid
and/or of coolant in the space by means of the sealing system. This
is where the labyrinth sealing system provides its sealing function
particularly efficiently. As a result, any thermal stresses
resulting from impeded thermal expansion of rotor components which
adjoin one another in the event of temperature differences are
reduced. The blade root of a rotor blade and the receiving
structure of the rotor which receives the rotor blade and fixes it
can therefore be produced with significantly lower tolerances. A
lower tolerance has an advantageous effect on the mechanical
installation stability of the rotor blade and the quiet running of
the rotor. In particular, form fits which are provided for the
purpose of securing the blade root in the receiving structure can
be provided with a lower clearance, which also correspondingly
reduces possible leaking flows through the form fit.
A further advantage is the ease of producing and installing the
sealing system. Since the sealing system having the labyrinth
sealing system is provided on the circumferential face, it is not
necessarily fixedly coupled to a rotor blade. Installation or
repair work on a rotor blade, such as for example, exchanging a
rotor blade, can therefore be carried out without great difficulty.
The sealing system remains unaffected by this work and can
therefore be used a number of times.
In a preferred configuration of the turbomachine, the rotor has a
rotor disk, which comprises the circumferential face and the
receiving structure, the circumferential face having a first
circumferential-face edge and a second circumferential-face edge,
which lies opposite the first circumferential-face edge along the
axis of rotation, the receiving structure having a first rotor-disk
groove and a second rotor-disk groove, which is at a distance from
the first rotor-disk groove in the circumferential direction of the
rotor disk, and the blade root of the first rotor blade being
inserted into the first rotor-disk groove and the blade root of the
second rotor blade being inserted into the second rotor-disk
groove.
Therefore, the securing of the rotatable rotor blade is such that,
when the turbomachine is operating, it is able to absorb the blade
stresses caused by flow and centrifugal forces and by blade
vibrations with a high degree of reliability and to transmit the
forces which arise to the rotor disk and ultimately to the entire
rotor. The rotor blade can be secured, by way of example, by axial
grooves, each rotor blade being clamped individually in a dedicated
rotor-disk groove which extends substantially in the axial
direction. For low loads, e.g. in the case of axial compressor
rotor blades of compressors, simple ways of securing the rotor
blade, for example using a dovetail or Laval root, are possible.
For steam-turbine end stages with long rotor blades and
correspondingly high blade centrifugal forces, as well as the
so-called plug-in root, the axial fir-tree root is also suitable.
The axial fir-tree securing is preferably also employed for rotor
blades which are subject to high thermal stresses in gas
turbines.
In the preferred configuration described above, the circumferential
face has a first circumferential-face edge and a second
circumferential-face edge as partial regions. Based on the
direction of flow of a flowing hot action fluid, in particular of
the hot gas in a gas turbine, in this case, by way of example, the
first circumferential-face edge is arranged upstream and the second
circumferential-face edge is arranged downstream. Depending on the
particular design details and requirements with regard to the
sealing action to be achieved, this geometric division allows a
configuration and arrangement of the sealing system over various
partial regions of the circumferential face.
The sealing system is preferably arranged on the first
circumferential-face edge and/or on the second circumferential-face
edge. The labyrinth sealing system may be arranged at least
partially on the first and/or second circumferential-face edge.
Arranging the sealing system on the first, for example upstream,
circumferential-face edge primarily limits the penetration of
flowing hot action fluid into the space and therefore prevents
damage to the rotor blade. Arranging the sealing system on the
second, downstream circumferential-face edge serves predominantly
to prevent the escape of coolant, for example cooling air which is
under a certain pressure in the space, in the axial direction along
the circumferential face over the second circumferential-face edge
into the flow passage. Since the hot action fluid expands in the
direction of flow, the pressure of the hot action fluid is
continuously reduced in the direction of flow. A coolant which is
under a certain pressure in the space will therefore escape from
the space in the direction of the lower ambient pressure, i.e. at
the downstream circumferential-face edge. Arranging the sealing
system having the labyrinth sealing system on the first
circumferential-face edge and on the second circumferential-face
edge closes off the space and accordingly offers highly reliable
protection both against the penetration of hot action fluid into
the space and the escape of coolant from the space.
Preferably, a circumferential-face central region, which is
bordered in the axial direction by the first circumferential-face
edge and the second circumferential-face edge, is formed on the
circumferential face, the sealing system being arranged at least
partially on the circumferential-face central region. In this case,
the labyrinth sealing system is preferably arranged on the
circumferential-face central region. The circumferential-face
central region forms a partial region of the circumferential face.
Therefore, there are various options for arranging the sealing
system on various partial regions of the circumferential face
together with the first and second circumferential-face edges.
Depending on design details and requirements with regard to the
sealing action to be achieved, it is possible to determine a
suitable solution, with the sealing system arranged on various
partial regions. Combinations of various partial regions are also
conceivable when arranging the sealing system. Therefore, with
regard to adapting to specific requirements in terms of the sealing
action to be achieved, the sealing system described offers a very
high degree of flexibility.
The sealing system having the labyrinth sealing system preferably
has a sealing element which extends in the circumferential
direction. The space extends substantially in the radial and axial
directions and in the circumferential direction of the rotor. A
sealing element which extends along the circumferential direction
of the rotor in the space is particularly suitable for preventing
the possibility of axial leaking flows of coolant and/or also of
hot action fluid with a high degree of efficiency. For example, an
axial leaking flow in the upstream direction, for example a hot gas
leaking out of the flow passage of a gas turbine, which spreads out
along the circumferential face is effectively prevented by the
sealing element. In this case, the leaking flow is delayed by the
obstacle in the space and ultimately comes to a standstill on that
side of the sealing element which faces the leaking flow (simple
restrictor). That side of the sealing element which is remote from
the leaking flow and that part of the space which adjoins it in the
axial direction are already effectively protected from being
exposed to the leaking medium, e.g. hot action fluid or coolant, by
the simple sealing element. The way in which the sealing element
operates can therefore be similar to the way in which the labyrinth
sealing system operates, and this enhances the sealing action.
A considerable improvement to the simple solution described above
with a sealing element extending in the circumferential direction
results from combining the sealing element with one or more further
sealing elements. In a preferred configuration, at least one
further sealing element is provided, which extends in the
circumferential direction and is arranged at an axial distance from
the sealing element. This multiple arrangement of sealing elements
considerably reduces possible leaking flows in the space. In
particular, it is possible, for example, for the sealing element to
be arranged on the first circumferential-face edge and for the
further sealing element to be arranged on the second
circumferential-face edge. As a result, the space is sealed both
upstream and downstream with respect to axial leaking flows. The
space is in particular protected very effectively against the
possibility of the penetration of hot action fluid both from the
upstream region at higher pressure and from the downstream region
at lower pressure in the flow passage. At the same time, the sealed
space can be used effectively by a coolant, e.g. cooling air. The
coolant is fed to the space under pressure and is used primarily
for efficient internal cooling of the highly thermally stressed
rotor, the blade platform and the main blade which radially adjoins
the blade platform.
A further advantageous use for the pressurized coolant in the space
includes in utilizing its barrier action with respect to the hot
action fluid in the flow passage. The design of the sealing
elements and the selection of the pressure of the coolant in the
space mean that the pressure difference between the coolant and the
hot action fluid is adequately low yet sufficiently high to achieve
a barrier action with respect to the hot action fluid. For this
purpose, the pressure of the coolant which prevails in the space
must be only slightly above the upstream pressure of the hot action
fluid. The greater the sealing action of the sealing elements, the
smaller any residual leaking flows of coolant into the flow passage
become.
At least the labyrinth sealing system is preferably produced
integrally in the sealing system, in particular by removing
material from the rotor disk. If the sealing system is designed,
for example, as a single labyrinth sealing system, it is produced
just by means of at least two sealing elements on the
circumferential surface, which extend in the circumferential
direction of the rotor disk and are at an axial distance from one
another. These sealing elements may be formed by metal restrictor
plates which are turned out of the solid. The integral production
method has the advantage that there is no need for an additional
joining element between the labyrinth sealing system and the
circumferential face. Therefore, in terms of process engineering,
the rotor disk can be machined and the labyrinth sealing system
produced in a single step carried out on a lathe, which is very
inexpensive. Furthermore, thermally induced stresses between the
rotor disk and the labyrinth sealing system do not play any role,
since only one material is used. Alternative configurations of the
sealing element, for example by means of a metal restrictor plate
welded onto the rotor disk or by means of a metal restrictor plate
which is jammed into a groove into the circumferential face, are
also possible.
On its outer radial end, the sealing element preferably has a
sealing point, in particular a knife edge. Residual leaking flows
through the space are decisively influenced by the sealing gap
width which can be achieved, i.e. for example the distance between
the outer radial end of the sealing element and the adjoining blade
platform which is to be sealed. To make the sealing gap width as
small as possible, it is provided for the outer radial end of the
sealing element to be sharpened. In this case, it is possible, in
particular to bridge the sealing gap, by producing the sealing
point or the knife edge with a small dimension compared to the
radial installation dimension of the blade platform. By drawing the
sealing tip or the knife edge onto the blade platform, the sealing
gap is bridged when the rotor blade is inserted into the receiving
structure, for example into an axial groove in a rotor disk. In
this way, the sealing gap is closed off, an improved seal is
achieved and the axial leaking flow is further reduced. Compared to
conventional designs, therefore, it is also possible to
considerably reduce the installation dimension of a rotor blade in
the receiving structure. The minimum installation dimension which
has hitherto been customary of between approximately 0.3 and 0.6 mm
can be reduced to approximately 0.1 to 0.2 mm by means of the new
design, i.e. is reduced by approximately two thirds.
The labyrinth sealing system preferably comprises the sealing
element and/or the further sealing element. The sealing element and
the further sealing element are therefore part of the labyrinth
sealing system. The labyrinth sealing system is preferably designed
as a labyrinth gap sealing system. In a preferred configuration, a
gap sealing element is provided for sealing a substantially axially
extending gap, the gap being formed between the blade platform of
the first rotor blade and the blade platform of the second rotor
blade and being in flow communication with the space. The gap
sealing element prevents a leaking flow through the gap. A leaking
flow of this type is substantially radially directed and may be
oriented both radially outward from the space through the gap and
radially inward through the gap into the space.
In this case, various designs are possible: For example, if the
flow passage of the turbomachine, e.g. of a compressor or a gas
turbine, adjoins the gap in the radially outward direction, the gap
sealing element prevents the penetration of the action fluid, e.g.
of the hot gas in a gas turbine, radially inward into the space
through the gap. As a result, the rotor, in particular the rotor
blade, is protected from oxidizing and/or corrosive attack in the
space. At the same time the gap sealing element prevents coolant,
e.g. cooling air, from escaping from the space through the gap
radially outward into the flow passage. In an alternative
configuration, a cavity may also adjoin the gap on the radially
outer side, this cavity being formed by the first and second rotor
blades which adjoin one another in the circumferential direction
(known as the box design of a rotor blade). In this case, the gap
sealing element firstly prevents the possibility of hot action
fluid penetrating from the space through the gap radially outward
into the cavity. Secondly, the cavity which is sealed by the gap
sealing element can be acted on by a coolant, e.g. cooling air.
This coolant is under pressure in the cavity and is available, for
example, for efficient internal cooling of the rotor blade which is
subject to high thermal loads or for other cooling purposes. A
further advantageous use of the pressurized coolant in the cavity
consists in utilizing its barrier action with respect to the hot
action fluid in the flow passage.
The gap sealing element is preferably produced by a metal gap
sealing plate which has a gap-sealing edge which engages in the gap
under the action of centrifugal force and closes off the gap.
Designing the gap sealing element as a metal gap sealing plate
represents a simple and inexpensive solution. In this case, for
example, a design as a thin metal strip which has a longitudinal
axis and a transverse axis is possible. In this case, the
gap-sealing edge extends substantially centrally on the metal strip
along the longitudinal axis and can be produced in a simple way by
bending over the metal strip. The gap sealing element is
expediently arranged in the space. When the turbomachine is
operating, the gap sealing element is then, as a result of the
rotation, pressed firmly by the radially outwardly directed
centrifugal force against the mutually adjoining blade platform,
the gap-sealing edge engaging in the gap and effectively sealing
the latter.
The gap sealing element is preferably made from a highly
heat-resistant material, in particular from a nickel-base or
cobalt-base alloy. Moreover, these alloys also have sufficient
elastic deformation properties. The material of the gap sealing
element is selected to match the material of the rotor, with the
result that contamination or diffusion damage is avoided.
Furthermore, uniform thermal expansion or contraction of the rotor,
in particular of the blade platform of the rotor blade, is
ensured.
The gap sealing element preferably radially adjoins the sealing
system. The combination of the gap sealing element with a sealing
system arranged on the circumferential face, in particular with a
labyrinth sealing system, results in particularly effective sealing
of the space against the possibility of leaking flows of hot action
fluid and/or of coolant. In particular, as a result a centrifugally
assisted sealing action of the gap sealing element is retained in
order to seal an axially extending gap. In this combination, the
sealing system reduces the substantially axially oriented leaking
flows, while the gap sealing element reduces the substantially
radially directed leaking flows. Furthermore, this separation of
functions readily allows flexible design adjustment to different
rotor geometries. Consequently, the gap sealing element and the
sealing system complement one another very effectively.
In a further preferred configuration, the sealing element engages
in a recess, in particular in a groove, in the circumferential
face. In this variant, the sealing element is not necessarily a
part of the labyrinth system, but it is part of the sealing system.
The sealing element is prevented from falling out and/or from being
thrown out under the action of centrifugal forces in steady-state
operation or in the event of a transient load on the turbomachine
is achieved by the fact that the sealing element engages in a
suitable recess. Furthermore, the recess produces a sealing
surface, which is expediently designed as a partial area of the
recess, on the circumferential face. In the case of a groove, this
sealing surface is formed, for example, at the base of the groove.
To achieve the optimum sealing action when the sealing element is
active, the sealing surface is produced with a suitably low and
well-defined surface roughness. After the actual production of the
groove, for example by abrading material from the circumferential
face by means of a milling or turning operation, a sealing surface
with the desired roughness can be produced on the base of the
groove by polishing.
The sealing element is preferably moveable in the radial direction.
This has the effect of causing the sealing element to move away
from the axis of rotation of the rotor in the radial direction
under the action of centrifugal force. This property is
deliberately exploited in order to achieve a significantly improved
sealing action at the blade platform of a rotor blade. Under the
action of centrifugal force, the sealing element comes into contact
with the blade platforms which are at a radial distance from the
circumferential face and adjoin one another in the circumferential
direction and is pressed firmly onto the blade platforms. The
radial mobility of the sealing element can be ensured by suitable
dimensioning of the recess and of the sealing element. Furthermore,
it is advantageous that, as a result, the sealing element can be
removed and, if appropriate, exchanged without problems for any
maintenance to be carried out or in the event of failure of the
rotor blade without using additional tools and without the risk of
the sealing element becoming stuck as a result of oxidizing or
corrosive attack under high operating temperatures. Furthermore, a
certain tolerance of the sealing element which engages in the
recess, in particular in the groove, is very useful, since as a
result thermal expansion is permitted, and therefore thermally
induced stresses are avoided in the rotor.
The sealing element preferably comprises a first partial sealing
element and a second partial sealing element, the first partial
sealing element and the second partial sealing element engaging in
one another. The partial sealing elements may be designed in such a
way that they provide, in a particular manner, a partial sealing
function for different regions in the space which are to be sealed.
These different regions in the space are formed, for example, by
suitable sealing surfaces at the base of the groove, on the blade
platform of the first rotor blade or on the blade platform of the
second rotor blade. As a result of being arranged as a pair of
partial sealing elements, the partial sealing elements combine to
form one sealing element, the sealing action of the pair being
greater than that of a single partial sealing element. By suitably
adapting the design of the partial sealing elements to the partial
regions in the space which are to be sealed, it is possible for the
sealing action of the paired partial sealing elements to be greater
than that which can be achieved, for example, with a single-piece
sealing element.
Preferably, the first partial sealing element and the second
partial sealing element can move in the circumferential direction
relative to one another. This provides a matched system comprising
partial sealing elements. The relative movement of the partial
sealing elements in the circumferential direction allows matched
engagement of the partial sealing elements in one another as a
function of the thermal and/or mechanical loads acting on the
rotor. The matched system of partial sealing elements may be
designed in such a way that under the action of the external
forces, such as for example the centrifugal force and the normal
and bearing forces, it to a certain extent adjusts itself in order
to provide its sealing action. Furthermore, possible thermally or
mechanically induced stresses are compensated for significantly
more successfully by the movable pair of partial sealing
elements.
In a preferred configuration, the first partial sealing element and
the second partial sealing element each have a disk-sealing edge,
which adjoins the circumferential face, and a platform-sealing
edge, which adjoins the blade platform. In this case, the
platform-sealing edge may in each case be further functionally
divided into partial platform-sealing edges. By way of example, for
a partial sealing element there may be a first partial
platform-sealing edge and a second partial platform-sealing edge,
the first partial platform-sealing edge being adjacent to the blade
platform of the first rotor blade and the second partial
platform-sealing edge being adjacent to the blade platform of the
second rotor blade. This functional division makes it easy to adapt
the design of the partial sealing elements to the particular
installation geometry of the first and second rotor blades in the
receiving structure. Suitable designing of the partial sealing
element ensures that the disk-sealing edge is sealed against the
circumferential face and the platform-sealing edge is sealed
against the blade platform of the rotor blade, producing the best
possible form fit.
The paired arrangement of the first and second partial sealing
elements to form a sealing element provides a particularly
effective seal. The first and second partial sealing elements
preferably overlap one another, with the platform-sealing edge and
the disk-sealing edge of the first partial sealing element being
adjacent to the platform-sealing edge and diskt-sealing edge,
respectively, of the second partial sealing element. As a result,
the paired arrangement of the two partial sealing elements produces
a good positive lock, and consequently the sealing element produces
a good seal against the penetration of hot action fluid into the
space and/or the escape of coolant into the flow passage.
The sealing element is preferably made from a highly heat-resistant
material, in particular from a nickel-base or cobalt-base alloy.
These alloys also have sufficient elastic deformation properties.
The result is that the material of the sealing element, in order to
avoid contamination or diffusion damage and to ensure a uniform
thermal expansion of the rotor, in particular of the blade platform
of the rotor blade, is selected to match the material of the
rotor.
In a preferred configuration, in the turbomachine with the rotor
extending along an axis of rotation, the receiving structure is
produced by a circumferential groove, the circumferential face
having a first circumferential face and a second circumferential
face which lies opposite the first circumferential face along the
axis of rotation, these faces in each case axially adjoining the
circumferential groove, the sealing system being provided in the
space on the first and/or second circumferential face.
When the turbomachine is operating, the means of securing the rotor
blades must with great reliability absorb the blade stresses caused
by flow and centrifugal forces and by the vibrations of the blade
and must transmit the forces which are generated to the rotor disk
and ultimately to the entire rotor. In addition to securing the
rotor blade in an axial groove, an arrangement in which the rotor
blade is secured in a circumferential groove is also in widespread
use, particularly for low and medium stresses. In this case,
various configurations are known depending on the stress (c.f. I.
Kosmorowski and G. Schramm, "Turbo Maschinen" [Turbomachines], ISBN
3-7785-1642-6, published by Dr. Alfred Huthig Verlag, Heidelberg,
1989, pp. 113-117). By way of example, for short rotor blades with
low centrifugal forces and bending moments, the so-called
hammerhead connection method, which is easy to produce, is used. In
the case of longer rotor blades and therefore higher blade
centrifugal forces, in the case of rotors of disk design,
particular design measures have to be used to prevent the rotor
disk from bending in the region of the first and second
circumferential faces at the level of the circumferential groove.
This can be achieved, for example, with the aid of a rotor disk
which is of solid design at the level of the circumferential
groove, a hooked hammerhead root or a hooked sliding root. However,
a more efficient transmission of forces to the rotor disk is
achieved, for example, by the circumferential fir-tree securing
means. In any event, the described concept for sealing the space
can be transferred very flexibly to a rotor in which the rotor
blade is secured in a circumferential groove.
The turbomachine is preferably a gas turbine.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is explained in more detail below, by way of example,
with reference to exemplary embodiments illustrated in the drawing,
in which, in some cases diagrammatically and in simplified
form:
FIG. 1 shows a half-section through a gas turbine with compressor,
combustion chamber and turbine,
FIG. 2 shows a perspective view of part of a rotor disk of a
rotor,
FIG. 3 shows a perspective view of part of a rotor disk with
inserted rotor blade,
FIG. 4 shows a side view of a rotor blade with sealing system,
FIGS. 5A-5D show various views of a first partial sealing element
of a sealing element illustrated in FIG. 4,
FIGS. 6A-6D show various views of a second partial sealing element
of a sealing element illustrated in FIG. 4,
FIG. 7 shows an axial plan view of part of a rotor with sealing
element,
FIG. 8 shows an axial plan view of part of a rotor with an
alternative configuration of the sealing element to that shown in
FIG. 7,
FIG. 9 shows a side view of a rotor blade with a labyrinth sealing
system,
FIG. 10 shows a side view of a rotor blade with an alternative
configuration of the labyrinth sealing system of that shown in FIG.
9,
FIG. 11 shows a perspective view of part of a rotor disk with
inserted rotor blade and with a gap sealing element,
FIG. 12 shows part of a view of the arrangement shown in FIG. 11,
on section line XII--XII,
FIG. 13 shows a perspective view of a rotor shaft with
circumferential grooves,
FIG. 14 shows a sectional view of part of a rotor with
circumferential groove and with inserted rotor blade,
FIG. 15 shows a sectional view of part of a rotor with an
alternative configuration of the rotor-blade securing to that shown
in FIG. 14.
In the individual figures, identical reference numerals have the
same meaning.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 shows a half-section through a gas turbine 1. The gas
turbine 1 has a compressor 3 for combustion air, a combustion
chamber 5 with burners 7 for a liquid or gaseous fuel, and a
turbine 9 for driving the compressor 3 and a generator, which is
not shown in FIG. 1. Fixed guide blades 11 and rotatable rotor
blades 13 are arranged in the turbine 9 on respective rings, which
extend radially and are not shown in the half-section, along the
axis of rotation 15 of the gas turbine 1. A pair of a ring of guide
blades 11 (guide-blade ring) and a ring of rotor blades 13
(rotor-blade ring) which follow one another along the axis of
rotation 15 are referred to as a turbine stage. Each guide blade 11
has a blade platform 17 which is arranged on the inner turbine
casing 19 in order to fix the corresponding guide blade 11. The
blade platform 17 represents a wall element in the turbine 9. The
blade platform 17 is a component which is subject to high thermal
loads and forms the outer boundary of the flow passage 21 in the
turbine 9. The rotor blade 13 is attached to the turbine rotor 23,
which is arranged along the axis of rotation 15 of the gas turbine
1, by means of a corresponding blade platform 17. The turbine rotor
23 may be assembled, for example, from a plurality of rotor disks
which are not shown in FIG. 1, receive the rotor blades 13, are
held together by a tie rod (not shown) and are centered, in such a
manner that they are able to tolerate thermal expansion, on the
axis of rotation 15 by means of radial serrations. Together with
the rotor blades 13, the turbine rotor 23 forms the rotor 25 of the
turbomachine 1, in particular of the gas turbine 1.
In the region of the gas turbine 1, air L is sucked in from the
environment. The air L is compressed in the compressor 3 and as a
result is simultaneously preheated. In the combustion chamber 5,
the air L is brought together with the liquid or gaseous fuel and
is burned. A fraction of the air L which has been removed from the
compressor 3 at suitable removal device 27 is used as cooling air K
to cool the turbine stages, the first turbine stage being exposed,
for example, to a turbine inlet temperature of approximately
750.degree. C. to 1200.degree. C. Expansion and cooling of the hot
action fluid A, referred to below as hot gas A, which flows through
the turbine stages and in the process sets the rotor 25 in
rotation, take place in the turbine 9.
FIG. 2 shows a perspective view of part of a rotor disk 29 of a
rotor 25. The rotor disk 29 is centered along the axis of rotation
15 of the rotor 25. The rotor disk 29 has a receiving structure 33
for rotor blades 13 of the gas turbine 1 to be secured in. The
receiving structure 33 is produced by recesses 35, in particular by
grooves, in the rotor disk 29. The recess 35 is in this case
designed as an axial rotor-disk groove 37, in particular as an
axial fir-tree groove. The rotor disk 29 has a circumferential face
31 which is arranged at the outer radial end of the rotor disk 29.
A first circumferential-face edge 39A and a second
circumferential-face edge 39B are formed on the circumferential
face 31. The first circumferential-face edge 39A lies opposite the
second circumferential-face edge 39B on the circumferential face 31
along the axis of rotation 15. A circumferential-face central
region 41, which in the axial direction is bordered by the first
circumferential-face edge 39A and the second circumferential-face
edge 39B, is formed on the circumferential face 31.
A perspective view of part of a rotor disk 29 with inserted rotor
blade 13A is illustrated in FIG. 3. The rotor disk 29 has
rotor-disk grooves 37A, 37B, which are open toward its
circumferential face 31, over its entire circumference; these
grooves run substantially parallel to the axis of rotation 15 of
the rotor 25, although they may also be inclined with respect to
this axis. The rotor-disk grooves 37A, 37B are provided with
undercuts 59. The blade root 43A of a rotor blade 13A is inserted
into a rotor-disk groove 37A along the insertion direction 57 of
the rotor-disk groove 37A. The blade root 43A is supported, by
means of longitudinal ribs 61, against the undercuts 59 of the
rotor-disk groove 37A. In this way, when the rotor disk 29 rotates
about the axis of rotation 15, the rotor blade 13A is held securely
with regard to the centrifugal forces which occur in the direction
of the longitudinal axis 47 of the rotor blade 13A. In the radially
outward direction, along the longitudinal axis 47 of the blade root
43A, the rotor blade 13A has a widened region, known as the blade
platform 17A.
The blade platform 17A includes a disk-side base 63 and an outer
side 65 which is on the opposite side from the disk-side base 63.
On the outer side 65 of the blade platform 17A there is a main
blade 45 of the rotor blade 13A. The hot gas A which is required
for operation of the rotor 25 flows past the main blade 45 and, in
the process, generates a torque on the rotor disk 29. At high
operating temperatures of the rotor 25, the main blade 45 of the
rotor blade 13A requires an internal cooling system, which is not
shown in FIG. 3.
In this case, a coolant K, for example cooling air K, is passed
through a feed line (not shown) through the rotor disk 29 into the
blade root 43A of the rotor blade 13A and, from there, to suitable
supply lines (likewise not shown in FIG. 3) of the internal cooling
system. To prevent the coolant K, in particular the cooling air K,
from escaping prematurely in the region of the blade root 43A and
of the blade platform 17, a sealing system 51 is provided.
The sealing system 51 is arranged on the circumferential face 31 on
the second circumferential-face edge 39B. The sealing system 51 has
a sealing element 53 which extends in the circumferential direction
of the rotor disk 29. A further sealing element 55 is provided and
extends in the circumferential direction of the rotor disk 29, at
an axial distance from the sealing element 53. The sealing element
53 and the further sealing element 55 each engage in a recess 35,
in particular in a groove, in the circumferential face 31.
The sealing system 51 seals the space 49 which is formed between
the blade platform 17A of the rotor blade 13A and a blade platform
17B of a second rotor blade 13B, which is illustrated by dashed
lines and is inserted into a second rotor-disk groove 37B, which is
at a distance from the first rotor-disk groove 37A in the
circumferential direction of the rotor disk 29, and the
circumferential face 31. This substantially prevents the hot gas A
from passing axially over the second circumferential-face edge 39B
into the space 49 and damaging the rotor blade 13A, 13B in the
region of the blade root 43A, 43B or the blade platform 17A, 17B.
Furthermore, coolant K is prevented from escaping from the space 49
in the axial direction along the circumferential face 31 over the
second circumferential-face edge 39B.
FIG. 4 shows a side view of a rotor blade 13 with sealing system
51. The sealing system 51 is illustrated as a partial section in
FIG. 4. The sealing system 51 is arranged on the first
circumferential-face edge 39A and on the second
circumferential-face edge 39B in the space 49. Based on the
direction of flow of the hot gas A, the first circumferential-face
edge 39A is located upstream on the circumferential face 31 of the
rotor disk 29, and the second circumferential-face edge 39B is
located downstream. The arrangement of the sealing system 51 on the
first, upstream circumferential-face edge 39A firstly restricts the
penetration of flowing hot gas A into the space 49. This prevents
damage to the rotor blade 13 and to the rotor disk 29 in the region
of the circumferential face 31.
Arranging the sealing system 51 on the second, downstream
circumferential-face edge 39B serves primarily to prevent as
efficiently as possible the escape of a coolant K, e.g. cooling air
K which is under a certain pressure in the space 49, in the axial
direction along the circumferential face 31 over the second
circumferential-face edge 39B into the flow passage. When the rotor
25 is operating, the hot gas A expands in the direction of flow. As
a result, the pressure of the hot gas A is continuously reduced in
the direction of flow. A coolant K which is under a certain
pressure in the space 49 will therefore escape from the space 49
toward the lower ambient pressure, i.e. at the downstream, second
circumferential-face edge 49B. The sealing system 51 on the first
circumferential-face edge 39A and on the second
circumferential-face edge 39B seals the space 49 in both
directions. Therefore, this design offers a particularly high
degree of protection both against the penetration of hot gas A into
the space 49 and against the escape of coolant K from the space
49.
On the first circumferential-face edge 39A, the sealing system 51
has a sealing element 53 which extends in the circumferential
direction of the rotor 29. The sealing element 53 engages in a
recess 35, in particular in a groove, which is machined into the
circumferential face 31. At the second circumferential-face edge
39B, the sealing system 51 has a sealing element 53 which extends
in the circumferential direction. A further sealing element 55 is
provided on the second circumferential-face edge 39B. The further
sealing element 55 extends in the circumferential direction of the
rotor disk 29 and is arranged at an axial distance from the sealing
element 53.
Forming the sealing system 51 by means of one or more sealing
elements 53, 55 is particularly suitable for more efficient
prevention of the possibility of axial leaking flows of coolant K
and/or of hot gas A in the space 49. For example, an axial leaking
flow directed upstream, e.g. of the hot gas A out of the flow
passage of a gas turbine 1, which flows into the space 49 over the
first circumferential-face edge 39A along the circumferential face
31, is effectively prevented from penetrating by the sealing
element 51 arranged on the first circumferential-face edge 39. At
the same time, an axial leaking flow which is directed out of the
space 49 along the second circumferential-face edge 39B is reliably
prevented from occurring by the obstacle in the form of the sealing
elements 53, 55.
This multiple arrangement of sealing elements 53, 55 considerably
reduces the possibility of leaking flows in the space 49.
Therefore, the sealed space 49 can be used efficiently for a
coolant K, e.g. cooling air K. This can be pressurized and can then
be used for efficient internal cooling of the rotor 25 which is
exposed to high thermal loads, in particular of the blade platform
17 and of the main blade 45 which adjoins the blade platform along
the longitudinal axis 47. A further advantageous use of the
pressurized coolant K in the space 49 is provided by the blocking
action with respect to the hot gas A in the flow passage. This
blocking action of the coolant K substantially prevents hot gas A
from penetrating into the space 49.
The sealing elements 53, 55 are each arranged so that they can move
in the radial direction in the recess 35, so that when the rotor 25
is operating, on account of the centrifugal force acting on the
sealing elements 53, 55, an improved sealing action compared to
conventional designs is achieved. The sealing elements 53, 55 will
move radially outward, parallel to the longitudinal axis 47, under
the action of centrifugal force. In the process, the disk-side base
63 of the blade platform 17 is very effectively sealed with respect
to possible axial leaking flows out of the space 49 or into the
space 49. The radial mobility of the sealing elements 53, 55 can be
provided by suitably designing the recess 35 and the sealing
elements 53, 55. As a result, the sealing elements 53, 55 can also
be removed and, if necessary, exchanged without problems for any
maintenance which may be required or in the event of a failure of
the rotor blade 13, without having to use additional tools and
without the risk of the sealing element 53 becoming jammed as a
result of an oxidizing or corrosive attack at high operating
temperatures.
Furthermore, a certain tolerance of the sealing elements 53, 55
which in each case engage in a recess 35, in particular in a
groove, is very advantageous. This allows thermal expansion and
therefore prevents thermally induced stresses. The sealing element
53, 55 has a first partial sealing element 67A and a second partial
sealing element 67B. The first partial sealing element 67A and the
second partial sealing element 67B engage in one another. By means
of their paired arrangement, the partial sealing elements 67A, 67B
complement one another to form a sealing element 53, 55 in a
particular way, the sealing action achieved by the paired partial
sealing elements 67A, 67B being greater than that achieved by an
individual partial sealing element 67A, 67B. A particularly
advantageous configuration of the partial sealing elements 67A, 67B
on the regions in the space 49 which are to be sealed in each case
ensures that the sealing action achieved by the paired arrangement
is greater than that which could be achieved with, for example, a
single-piece sealing element 53. A possible, particularly
advantageous configuration of the partial sealing elements 67A, 67B
is described below with reference to FIGS. 5A to 5D and FIGS. 6A to
6D.
The sealing element 53, 55 shown in FIG. 4 is, in a preferred
configuration, composed of two partial sealing elements 67A, 67B
which engage in one another. FIGS. 5A to 5D show various views of
the first partial sealing element 67A:
FIG. 5A shows a perspective view of the first partial sealing
element 67A. The first partial sealing element 67A has a
disk-sealing edge 69 and a platform-sealing edge 71 which lies
opposite the disk-sealing edge 69. In the installed state of the
partial sealing element 67A, the disk-sealing edge 69 adjoins the
circumferential face 31, and the platform-sealing edge 71 adjoins
the disk-side base 63 of the blade platform 17. FIG. 5B shows a
view of the disk-sealing edge 71 of the first partial sealing
element 67A, FIG. 5C shows a plan view of the first partial sealing
element 67A, and FIG. 5D shows a side view. The platform-sealing
edge 71 has a first partial platform-sealing edge 71A and a second
partial platform-sealing edge 71B. This dividing of the
platform-sealing edge 71 into two partial platform-sealing edges
71A, 71B makes it easy to adapt the design of the first partial
sealing element 67A to the particular installation geometry of a
rotor blade 13 and of a further rotor blade 13B in a rotor disk 29
(cf. FIG. 3 and FIG. 4).
The second partial sealing element 67B is designed in a
corresponding way. FIGS. 6A to 6D show various views of the second
partial sealing element 67B of a sealing element 53 illustrated in
FIG. 4. In a similar way to the first partial sealing element 67A,
the second partial sealing element 67B has a disk-sealing edge 69
and a platform-sealing edge 71 which lies opposite the disk-sealing
edge 69. In this case, the platform-sealing edge 71 is further
divided in functional terms into partial platform-sealing edges
71A, 71B. A first partial platform-sealing edge 71A and a second
partial platform-sealing edge 71B are provided. Each of the partial
sealing elements 67A, 67B is designed in such a way that its center
of gravity is arranged adjacent to precisely one of the partial
platform-sealing edges 71A, 71B assigned to the corresponding
partial sealing element 67A, 67B. This is achieved by means of a
stepped design of each of the partial sealing elements 67A, 67B,
with a region of reduced material thickness and a region of greater
material thickness, each region being assigned to precisely one
partial platform-sealing edge 71A, 71B.
The result of this design of the partial sealing elements 67A, 67B
is that the disk-sealing edge 69 is well sealed against the
circumferential face 31 and the platform-sealing edge 71, or each
of the partial platform-sealing edges 71A, 71B, is/are sealed
against the blade platform 17 of the rotor blade 13, a form fit and
improved mechanical stability being produced. The first partial
sealing element 67A, and the second partial sealing element 67B are
arranged in pairs to form a sealing element 53. The result is a
very efficient seal.
The partial sealing elements 67A, 67B are designed in such a way
that, in the installed state, they engage in one another and
overlap one another, the platform-sealing edge 71 and the
disk-sealing edge 69 of the first partial sealing element 67A being
adjacent to the platform-sealing edge 71 and the disk-sealing edge
69, respectively, of the second partial sealing element 67B. The
partial sealing elements 67A, 67B are arranged in such a way that
regions of different material thickness come into contact with one
another. Therefore, the paired arrangement of the two partial
sealing elements 67A, 67B produces a very good form fit, and
consequently the sealing element 53 achieves a good seal against
the penetration of hot gas A into the space 49 and/or the escape of
coolant K into the flow passage (cf. FIG. 4). The partial sealing
elements 67A, 67B are in the form of, for example, of metallic
sealing plates. The material selected is able to withstand high
temperatures and has sufficient elastic deformation properties.
Examples of suitable materials are a nickel-base alloy or a
cobalt-base alloy. This ensures that the material of the partial
sealing elements 67A, 67B is selected to match the material of the
rotor 25. As a result, contamination or diffusion damage is avoided
and uniform, substantially stress-free thermal expansion of the
rotor 25 is possible.
FIG. 7 shows an axial plan view of part of a rotor 25 with a
sealing element 53. The rotor 25 has a rotor disk 29. The rotor
disk 29 has a first rotor-disk groove 37A and a second rotor-disk
groove 37B, which is arranged at a distance from the first
rotor-disk groove 37A in the circumferential direction of the rotor
disk 29. A first rotor blade 13A and a second rotor blade 13B are
inserted into the rotor disk 29, the blade root 43A of the first
rotor blade 13A being inserted into the rotor-disk groove 37A, and
the blade root 43B of the second rotor blade 13B engaging in the
second rotor-disk groove 37B. The blade platform 17A of the first
rotor blade 13A adjoins the blade platform 17B of the second rotor
blade 13B, and a space 49 is formed between the blade platforms
17A, 17B and the circumferential face 31.
A sealing element 53 is provided in the space 49 on the
circumferential face 31. The sealing element 53 has a disk-sealing
edge 69 and a first partial platform-sealing edge 71A and a second
partial platform-sealing edge 71B lying opposite the disk-sealing
edge 69. The sealing element 53 is inserted into a recess 35, in
particular into a groove in the circumferential face 31. The
disk-sealing edge 69 adjoins the circumferential face 31. The first
partial platform-sealing edge 71A adjoins the disk-side base 63 of
the first blade platform 17A, and the second partial
platform-sealing edge 71B adjoins the disk-side base 63 of the
second blade platform 17B.
The sealing element 53 may be produced by two paired partial
sealing elements 67A, 67B which engage in one another and can move
in the radial and circumferential directions, as explained in FIGS.
5A to 5D and in FIGS. 6A to 6D. This allows particularly efficient
sealing of the space 49. In particular, axially directed leaking
flows out of the space 49 or into the space 49 are effectively
prevented.
When the rotor 25 is rotating, the sealing element 53 will move
radially outward, away from the axis of rotation 15 of the rotor
25, parallel to the longitudinal axis 47 under the action of
centrifugal force. This effect is used to achieve a significantly
improved sealing action at the mutually adjoining blade platforms
17A, 17B of the adjacent rotor blades 13A, 13B. The sealing element
53 or each of the paired partial sealing elements 67A, 67B (not
shown in FIG. 7, but cf. FIGS. 5A-5D and 6A-6D), under the action
of centrifugal force, comes into contact with the blade platforms
17A, 17B which are at a radial distance from the circumferential
face 31 and are adjacent to one another in the circumferential
direction, and is pressed firmly onto the disk-side base 63 of
these platforms.
Suitable dimensioning of the recess 35, in particular of the
groove, and of the sealing element 53 ensures sufficient radial
mobility. In addition, it is provided for the sealing element 53 to
be able to move in the circumferential direction of the rotor disk
29. The sealing element 53, in particular each of the partial
sealing elements 67A, 67B (which are not shown in FIG. 7, but cf.
FIGS. 5A-5D and FIGS. 6A-6D), will then adjust itself under the
action of all the external forces, such as for example the
centrifugal force and also the normal and/or bearing forces, in
order to provide its sealing action. The inclination of the partial
platform-sealing edges 71A, 71B with respect to the longitudinal
axis 47 corresponds to the inclination of the disk-side base 63 of
the blade platforms 17A, 17B. The result is a good form fit and, on
account of the inclination with respect to the longitudinal axis
47, a distribution of forces over the sealing element 53 and the
adjoining disk-side base 63, which is advantageous for the sealing
action. Installation conditions may lead to a gap 73 forming
between the adjacent platforms 17A, 17B. This gap 73 is in flow
communication with the space 49 and can if appropriate be sealed by
means of a simple gap seal element (cf. FIG. 11 and the description
associated with this figure).
An axial plan view of part of a rotor 25 with an alternative
configuration of the sealing element 53 to that shown in FIG. 7 is
illustrated in FIG. 8. The blade platform 17A of the first rotor
blade 13A is offset in the radial direction with respect to the
adjoining blade platform 17B of the second rotor blade 13B. An
offset .delta. of this type between blade platforms 17A, 17B which
adjoin one another in the circumferential direction generally
occurs, for installation reasons, when the rotor-disk grooves 37A,
37B are inclined with respect to the axis of rotation 15 of the
rotor 25. The sealing element 53, or each of the partial sealing
elements 67A, 67B arranged in pairs to form the sealing element 53
(this arrangement is not shown in FIG. 7, but cf. FIGS. 5A-5D and
FIGS. 6A-6D), is equipped with an offset-sealing edge 75, which
seals the offset .delta. in a positively locking manner. The
sealing concept described can therefore be flexibly applied to
various rotor geometries and installation dimensions by suitably
designing the sealing element 53.
FIG. 9 shows a side view of a rotor blade 13 which is inserted in a
rotor disk 29, the sealing system 51 being arranged in the space 49
on the circumferential-face central region 41 of the
circumferential face 31. The sealing system 51 is in this case
designed as a labyrinth sealing system 51A, in particular a
labyrinth gap sealing system 51A. The labyrinth gap sealing system
51A is produced by a plurality of sealing elements 53, which extend
in the circumferential direction of the rotor disk 29 and are
spaced apart from one another in the axial direction, on the
circumferential-face central region 41. The individual sealing
elements 53 are in this case each formed by a metal restrictor
plate 77A-77E jammed into the circumferential face 41. The action
of the labyrinth gap sealing system 51A produced by the various
metal restrictor plates 77A-77E is based on restricting a flowing
hot gas A and/or a coolant K as efficiently as possible in the
sealing system 51A and, as a result, substantially reducing an
axially directed leaking flow through the space 49. The outer
radial end 79 of a metal restrictor plate 77A is spaced apart from
the disk-side base 63 of the blade platform 17 by a sealing gap 81.
A residual leaking flow in the space 49 may arise through the seal
gap 81, as is generally the case with labyrinth gap seals 51A. By
suitably designing and arranging the metal restrictor plates
77A-77E of the labyrinth gap sealing system 51A, the residual
leaking flow is limited to a predetermined level. Compared to other
possible labyrinth sealing systems, the labyrinth gap sealing
system 51A has the advantage that the sealing gaps 81 produce a
tolerance with respect to thermally and/or mechanically induced
relative expansions in the rotor 25.
An alternative configuration to the sealing system 51 shown in FIG.
9 is illustrated in FIG. 10. The sealing system 51 is likewise
designed as a labyrinth gap sealing system 51A, in this case being
produced integrally, in particular by removing material from the
rotor disk 29. The labyrinth gap sealing system 51A is arranged on
the circumferential-face central region 41 of the rotor disk 29.
The labyrinth gap sealing system 51A has a plurality of sealing
elements 53 which extend in the circumferential direction of the
rotor disk 29 and are at an axial distance from one another. The
sealing elements 53 are produced by four metal restrictor plates
77A-77D which are turned out of the solid rotor disk 29. This
production method means that there is no need for an additional
connection element between the labyrinth gap sealing system 51A and
the circumferential face 31. This is also an inexpensive solution
in turns of process engineering. Furthermore, thermally induced
stresses between the rotor disk 29 and the labyrinth gap sealing
system 51A do not play a role, since only one material is used.
Other configurations of the sealing element 53, for example using a
metal restrictor plate 77A welded onto the rotor disk, are also
possible. At its outer radial end 79, the sealing element 53 has a
sealing tip 83, in particular a knife edge. The sealing gap 81 can
be reduced to the smallest possible size by sharpening the outer
radial end 79 of the sealing element 53. In this way, residual
leaking flows through the space 49 are reduced further. It is also
possible to bridge the sealing gap, by producing the sealing point
83 or the knife edge with a slight oversize compared to the radial
installation dimension of the blade platform 17. By fitting the
sealing tip 83 or the knife edge onto the disk-side base 63 of the
blade platform 17, the sealing gap 81 is then bridged when the
rotor blade is inserted into the rotor disk 29. In this way, the
sealing gap 81 is virtually completely closed, a considerably
improved sealing action is achieved and a possible axial leaking
flow, for example caused by the flowing hot gas A or by a coolant
K, in the space 49 is further reduced.
FIG. 11 shows a perspective view of part of a rotor disk 29 with
inserted rotor blades 13A, with the blade root 43A of the rotor
blade 13A inserted in a first rotor-disk groove 37A. The blade root
43B of a second rotor blade 13B, which is illustrated in dashed
lines, is inserted in a second rotor-disk groove 37B and is
arranged adjacent to the rotor blade 13A in the circumferential
direction of the rotor disk 29. The sealing system 51, which is
designed as a labyrinth gap sealing system 51A, is arranged on the
circumferential face 31, on the circumferential-face central region
41. The sealing system 51A is produced by a plurality of sealing
elements 53 which are spaced apart from one another along the axis
of rotation 15 and extend in the circumferential direction of the
rotor disk 29.
Between the blade platform 17A of the rotor blade 13A and the blade
platform 17B of the second rotor blade 13B there is a substantially
axially extending gap 73 which is in flow communication with the
space 49. A gap sealing element 85 is provided for the purpose of
sealing the gap 73. The gap sealing element 85 is produced in a
simple way by means of a suitable metal gap sealing plate which has
a gap-sealing edge 87. The gap-sealing edge engages in the gap 73
under the action of centrifugal force and seals the gap 73. The gap
sealing element 85 is arranged in the space 49 in such a way that
it radially adjoins the sealing system 51, in particular the
labyrinth gap sealing system 51A. The gap sealing element 85
substantially prevents a leaking flow through the gap 73. A leaking
flow through the gap 73 of this type is substantially radially
directed and may be oriented both radially outward from the space
49 through the gap 73 and radially inward through the gap 73 into
the space 49.
A cavity 97 is formed by the platforms 17A, 17B, which adjoin one
another in the circumferential direction of the rotor disk 29, of
the rotor blades 13A, 13B. This cavity adjoins the gap 73 on the
radially outer side (box design of the rotor blades 13A, 13B). In
this case, the gap sealing element 85 on the one hand prevents the
possible penetration of hot gas A from the space 49 through the gap
73 radially outward into the cavity 97. Secondly, the cavity 97,
which is sealed by the gap sealing element 85, can be acted on by a
coolant K, e.g. by cooling air K. The coolant K is fed to the
cavity 97 under pressure, where it is available for efficient
internal cooling of the rotor blades 13A, 13B which are subject to
high thermal loads or for other cooling purposes. Furthermore, the
barrier action of a pressurized coolant K in the cavity 97 can be
used against the hot gas A in the flow passage.
In order to be able to withstand the high temperatures which occur
when the rotor 25 is operating and to be as resistant as possible
to the oxidizing and corrosive properties of the hot gas A, the gap
sealing element 85 is made from a highly heat-resistant material,
in particular from a nickel-base or cobalt-based alloy.
FIG. 12 shows part of a view of the arrangement shown in FIG. 11 on
section line XII--XII. The gap sealing element 85 is arranged in
the space 49 and adjoins the sealing element 53 in the radially
outward direction. When the rotor 25 is operating, the gap sealing
element 85, on account of the rotation, is pressed firmly onto the
disk-side base 63 of the mutually adjoining platforms 17A, 17B by
the centrifugal force which is directed radially outward along the
longitudinal axis 47, the gap sealing edge 87 engaging in the gap
73 and, as a result, substantially closing off the gap 73. The
combination of the gap sealing element 85 with the sealing system
51 on the circumferential face 41, in particular with the labyrinth
sealing system 51A (cf. FIG. 11), produces a particularly effective
sealing of the space 49 with respect to possible leaking flows of
hot gas A and/or of coolant K. In this combination, the sealing
system 51 substantially reduces the axially directed leaking flows,
while the gap sealing element 85 substantially reduces the radially
directed leaking flows (cf. FIG. 11). In this way, the gap sealing
element 85 and the sealing system 51 complement one another very
effectively.
In addition to a rotor blade 13 being secured in a substantially
axially directed rotor-disk groove 37 in a rotor disk 29, other
ways of securing the rotor blade are also known. The use of the
sealing system described for alternative means of securing the
rotor blade is illustrated below in FIGS. 13 to 15.
FIG. 13 shows a perspective view of a rotor shaft 89 of a rotor 25
which extends along an axis of rotation 15. A receiving structure
33 is produced by a plurality of circumferential grooves 91 which
are at an axial distance from one another, extend over the entire
circumference of the rotor shaft 89 and are machined into the
circumferential face 31. In this case, the circumferential face 31
has a first circumferential face 93 and a second circumferential
face 95, which lies opposite the first circumferential face 93
along the axis of rotation 15. The first circumferential face 93
and the second circumferential face 95 each axially adjoin a
circumferential groove 91.
FIG. 14 shows a sectional view of part of a rotor 25 with
circumferential groove 91 and with inserted rotor blade 13. The
circumferential groove 91 is produced as a hammerhead groove which
receives the blade root 43. This method of securing the blade is
preferably used for short rotor blades 13 which are subject to low
centrifugal forces and bending moments. A sealing element 53 is
provided in the space 49 on both the first circumferential face 93
and the second circumferential face 95. The sealing element 53
extends in the circumferential direction of the rotor shaft 89 and
engages in a recess 35, in particular in a groove, in the rotor
shaft 89. The sealing element 53 is arranged radially moveably in
the recess 35. When the rotor shaft 89 rotates about the axis of
rotation 15, the sealing element 53 will move radially outward
along the longitudinal axis 47 of the rotor blade 13, under the
action of centrifugal force, and will be pressed firmly onto the
disk-side base 63 of the blade platform 17. As a result, the space
49 is sealed. The sealing element 53 may be assembled from two
paired partial sealing elements 67A, 67B which engage in one
another and are not shown in FIG. 14 (cf. FIG. 4 and FIGS. 5A-5D
and 6A-6D).
FIG. 15 shows a sectional view of part of a rotor 25 with an
alternative configuration of the securing of the rotor blade to
that shown in FIG. 14. In this case, the circumferential groove 91
is produced by a so-called circumferential fir-tree groove.
Accordingly, the blade root 43 of the rotor blade 13 is produced as
a fir-tree root which engages in the circumferential groove 91, in
particular in the circumferential fir-tree groove. This method of
securing the rotor blade 13 produces very effective transmission of
forces to the rotor shaft 89 and particularly reliable holding when
the rotor 25 rotates about the axis of rotation 15. In a similar
manner to that shown in FIG. 14, a sealing element 53 for sealing
the space 49 is provided both on the first circumferential face 93
and on the second circumferential face 95 in the space 49.
The concept described for sealing the space 49 can in any event be
transferred very flexibly to a rotor 25 whose rotor blade 13 is
secured in a circumferential groove 91.
The invention being thus described, it will be obvious that the
same may be varied in many ways. Such variations are not to be
regarded as a departure from the spirit and scope of the invention,
and all such modifications as would be obvious to one skilled in
the art are intended to be included within the scope of the
following claims.
* * * * *